Hot wire machines are only used on certain types of foam, usually just the styrene-based ones (eg Styrofoam, EPS). Some other foam products produce toxic combustion products, so you can't cut them that way. What type of foam are you trying to cut?
The trouble with an oscillating blade type machine is that you need clearance under the piece being cut, or the blade is constantly banging against the spoilboard.
Is there really a compelling reason to do this in-house? The best way to cut foam materials is with a water-jet, but these machines are fairly expensive. If you're just trying to save money, maybe shopping around for a different shop to outsource to would make more sense than shopping for machines.